JP6417145B2 - Corneal imaging device - Google Patents

Description

The present invention relates to a cornea imaging apparatus that captures a cornea image by irradiating illumination light to a subject's eye and receiving reflected light from the cornea of the subject's eye.

Conventionally, the cell state of the cornea, particularly the corneal endothelium, has been observed when determining the presence or absence of an eye disease or diagnosing the postoperative course of the eye.

When observing the cell state of such corneal endothelium, a corneal imaging apparatus that can image corneal endothelial cells in a non-contact manner with respect to an eye to be examined is known. In this cornea photographing device, a slit-shaped illumination light is irradiated obliquely to the cornea of an eye to be examined by an illumination optical system, and reflected light from the cornea is received by an imaging optical system to image corneal endothelial cells. Yes.

By the way, since the corneal endothelial cell has a small thickness dimension, the corneal imaging apparatus has a problem that it is difficult to obtain a clear focused image of the corneal endothelial cell. In particular, since the corneal imaging apparatus employs slit-shaped illumination light, in order to avoid the adverse effects of reflected light from the corneal epithelium or corneal stroma and obtain a clear corneal endothelial cell, the illumination optical system and It is necessary to accurately align the in-focus position in the imaging optical system with the position of the corneal endothelial cell, and in particular, alignment in the Z direction (front-rear direction) with respect to the corneal endothelial cell is important.

In Patent Document 1, the corneal surface (corneal epithelium) is irradiated with alignment light, the reflected light (bright spot) is detected by an alignment detection sensor inside the main body, the XY position is aligned, and another alignment light is emitted. A method of acquiring a corneal endothelium (cell) image continuously at predetermined time intervals while entering the cornea of the eye to be examined obliquely, receiving a reflection image thereof with a one-dimensional CCD, and detecting a Z position from the received light signal. Is disclosed.

Japanese Patent No. 4916255

In the method disclosed in Patent Document 1, a plurality of sheets are continuously acquired at predetermined time intervals while moving forward (in the corneal epithelial direction) in the Z direction from a predetermined position at the rear (posterior chamber) of the focal position of the corneal endothelium image. An image is taken, and a good image is selected from a plurality of taken images using an image analysis process, etc., and the inspector performs Z-focusing and focusing without performing in-focus positioning. A corneal endothelium image at a position close to the focus position can be taken.

However, although the method of Patent Document 1 that continuously shoots at a predetermined time interval while moving forward in the Z direction (corneal epithelial direction) is easy to shoot near the in-focus position, it shoots at a predetermined time interval. It is difficult to image the focal position completely in accordance with the position of the corneal endothelial cell, or an XY misalignment occurs during the movement. As a result, a desired (high contrast) corneal endothelium image cannot be obtained. Imaging was performed from the beginning. As a result, there was a problem that the measurement time was long and the patient was burdened.

The present invention solves the above-described problem. Since the corneal endothelium image is photographed while detecting the in-focus position of the corneal endothelium image, even if the in-focus position is shifted due to a minute movement of the eye to be examined, the present invention is short. An object of the present invention is to provide a corneal imaging apparatus that can easily capture a high-contrast corneal endothelium image in a short time by performing Z alignment in time and adjusting the in-focus position.

In order to achieve the above object, an invention according to claim 1 is directed to an illumination optical system including an illumination light source that irradiates a slit light beam obliquely to the eye to be examined, and a reflected light beam from the cornea of the eye to be examined by the slit light beam. And an imaging optical system including a photoelectric element that picks up an image of the cornea and receives the light and drives the illumination optical system and the imaging optical system as a whole toward or away from the eye to be inspected. The corneal imaging apparatus having the means includes a light source and a light receiving element for detecting front and rear positions (positions of Z-axis coordinates), and the light receiving element receives reflected light from the cornea and epithelium of the eye to be examined, and reflects the endothelium. Control means for detecting the peak value of the signal and moving the apparatus back and forth (in the Z-axis direction) so that the peak position of the epithelial reflection signal moves to the predetermined position when the detected peak value is lower than the predetermined value. Features provided To.

The light receiving element such as a line sensor receives the reflected light from the corneal endothelium and epithelium of the eye to be examined. When the peak value of the reflected signal from the endothelium is equal to or greater than a predetermined value, the Z alignment is photographed as the focus range of the endothelium. When the peak value of the reflected signal of the epithelium is lower than a predetermined value, it is determined that the Z alignment is out of the focus range of the endothelium (occurrence of Z alignment deviation), and the peak position of the epithelial reflected signal is a predetermined position (for example, imaging Since the apparatus is moved in the Z direction so that the in-focus position of the optical system moves to a position of about 500 μm from the epithelium), the imaging optical system is always controlled to the in-focus position of the imaging optical system during imaging. As a result, the frequency of restarting imaging from the beginning can be reduced, so that the measurement time is shortened, the burden on the patient is reduced, and imaging is always possible at the in-focus position of the corneal endothelium image. It is easy to take a corneal endothelium image (with high contrast).

As described above, the corneal imaging device according to the present invention captures a corneal endothelium image while detecting the in-focus position of the corneal endothelium image. Therefore, even if the in-focus position is shifted due to a minute movement of the eye to be examined, the corneal endothelium image is short. Z-alignment is performed in time and the in-focus position is adjusted, so that high-contrast corneal endothelium images can be taken in a short time and easily. As a result, the burden on the patient is reduced and the endothelial cell image is reliably obtained. Can be taken.

BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing for demonstrating the optical system as one Embodiment of this invention. Explanatory drawing for demonstrating the cornea imaging device as one Embodiment of this invention. Explanatory drawing for demonstrating the control circuit etc. which are connected to the optical system shown in FIG. The flowchart which shows the imaging | photography procedure of a cornea imaging device. Explanatory drawing for demonstrating the anterior eye part displayed on a display screen. Explanatory drawing for demonstrating the reflected light beam in each layer of a cornea. Explanatory drawing which shows light quantity distribution detected by a light quantity detection means. Explanatory drawing for demonstrating the structure of each layer of a cornea. An explanatory view of a state of Z alignment when a subject's eye moves during corneal endothelium imaging, and reflection signals of the corneal epithelium and corneal endothelium in the line sensor.

Hereinafter, in order to clarify the present invention more specifically, embodiments of the present invention will be described in detail with reference to the drawings.

First, FIG. 1 shows an apparatus optical system 10 as an embodiment of a cornea photographing apparatus according to the present invention. The apparatus optical system 10 includes an imaging illumination optical system 14 and a position detection optical system 16 on one side with an observation optical system 12 for observing the anterior eye portion of the eye E to be examined, and a position detection illumination on the other side. The optical system 18 and the imaging optical system 20 are provided. In particular, in the present embodiment, the illumination optical system is configured to include the imaging illumination optical system 14 and the position detection illumination optical system 18.

The observation optical system 12 is configured such that a half mirror 22, an objective lens 24, a half mirror 26, a cold mirror 27, and a CCD 28 as a photoelectric element are provided on the optical axis O1 in order from a position close to the eye E. Further, a plurality (two in the present embodiment) of observation light sources 30 and 30 are arranged in front of the eye E to be examined. As the observation light sources 30, 30, for example, infrared LEDs that emit infrared light beams are used. The cold mirror 27 transmits infrared light while reflecting visible light, and the reflected light beam emitted from the observation light sources 30 and 30 and reflected by the anterior eye portion of the eye E is examined. The image is formed on the CCD 28 through the objective lens 24 and the cold mirror 27.

The imaging illumination optical system 14 includes a projection lens 32, a cold mirror 34, a slit 36, a condensing lens 38, and an imaging light source 40 in order from a position close to the eye E. The imaging light source 40 is, for example, an LED that emits a visible light beam. The cold mirror 34 transmits infrared light while reflecting visible light. Then, the light beam emitted from the imaging light source 40 is converted into a slit light beam through the objective lens 38 and the slit 36, reflected by the cold mirror 34, and then irradiated to the cornea C from the oblique direction through the projection lens 32. It is like that.

The position detection optical system 16 has a part of its optical axis aligned with the optical axis of the imaging illumination optical system 14, and is provided with a projection lens 32, a cold mirror 34, and a line sensor 44 in order from a position close to the eye E. Is configured. A light beam emitted from an observation light source 54 to be described later and reflected by the cornea C is imaged on the line sensor 44 through the projection lens 32 and the cold mirror 34.

On the other hand, the position detection illumination optical system 18 includes an objective lens 46, a cold mirror 48, a condenser lens 52, and an observation light source 54 as a position detection light source in order from a position close to the eye E. . As the observation light source 54, for example, an infrared light source such as an infrared LED is suitably employed. The infrared light beam emitted from the observation light source 54 is irradiated to the cornea C from an oblique direction. Note that the observation light source 54 may be configured by combining a visible light source such as a halogen lamp or visible light LED and an infrared filter, for example. However, the observation light source 54 is not necessarily an infrared light source, and a visible light source such as a halogen lamp or a visible light LED may be used. When a visible light source is used, the illuminance is preferably made smaller than the illuminance of the imaging light source 40. Thereby, it is possible to reduce the burden on the subject when irradiating the light beam from the observation light source 54 such as alignment.

The imaging optical system 20 has a part of its optical axis aligned with the optical axis of the position detection illumination optical system 18, and the objective lens 46, cold mirror 48, slit 56, magnification change in order from the position close to the eye E to be examined. A lens 58, a focusing lens 60, a cold mirror 27, and a CCD 28 are provided. Then, the light beam irradiated from the imaging light source 40 and reflected by the cornea C is reflected by the cold mirror 48 through the objective lens 46, and then converted into a parallel light beam by the slit 56. The light is reflected by the cold mirror 27 through the lens 60 and imaged on the CCD 28.

The half mirror 22 provided on the observation optical system 12 constitutes a part of the fixation target optical system 64 and the alignment optical system 66.

The fixation index optical system 64 includes a half mirror 22, a projection lens 68, a half mirror 70, a pinhole plate 72, and a fixation target light source 74 in order from a position close to the eye E. The fixation target light source 74 is a light source that emits visible light, such as an LED, and the light beam emitted from the fixation target light source 74 is transmitted through the pinhole plate 72 and the half mirror 70 and then converted into a parallel light beam by the projection lens 68. Then, it is reflected by the half mirror 22 and irradiated to the eye E.

The alignment optical system 66 includes a half mirror 22, a projection lens 68, a half mirror 70, a diaphragm 76, a pinhole plate 78, a condenser lens 80, and an alignment light source 82 in order from a position close to the eye E. . Infrared light is emitted from the alignment light source 82, and the infrared light is collected by the condenser lens 80, passes through the pinhole plate 78, and is guided to the diaphragm 76. The light that has passed through the diaphragm 76 is reflected by the half mirror 70, converted into a parallel light beam by the projection lens 68, reflected by the half mirror 22, and applied to the eye E.

Further, the half mirror 26 provided on the observation optical system 12 constitutes a part of the alignment detection optical system 84.

The alignment detection optical system 84 includes a half mirror 26 and an alignment detection sensor 88 capable of detecting the position in order from a position close to the eye E. The light beam emitted from the alignment light source 82 and reflected by the cornea C is reflected by the half mirror 26 and guided to the alignment detection sensor 88.

The apparatus optical system 10 having such a structure is accommodated in the cornea photographing apparatus 100 shown in FIG. The cornea photographing apparatus 100 is configured such that a main body 104 is provided on a base 102, and a case 106 is provided on the main body 104 so as to be movable back and forth, right and left, and up and down. The base 102 has a built-in power supply device and is provided with an operation stick 108 so that the case 106 can be driven by operating the operation stick 108. Further, the main body unit 104 accommodates control circuits and the like described later, and a display screen 110 including a liquid crystal monitor, for example.

Further, as shown in FIG. 3, the cornea photographing apparatus 100 is provided with a driving unit that moves the apparatus optical system 10 toward or away from the eye E by driving the case 106. . These driving means are constituted by, for example, a rack and pinion mechanism, and in this embodiment, an X-axis driving mechanism 112 that drives the apparatus optical system 10 in the vertical X direction in FIG. 3, and a paper surface in FIG. A Y-axis drive mechanism 114 that drives in the vertical Y direction and a Z-axis drive mechanism 116 that drives in the left-right Z direction in FIG. 3 are provided.

Further, the cornea photographing apparatus 100 is provided with an imaging control circuit 117 serving as an imaging control unit that performs operation control of imaging of the cornea image by the apparatus optical system 10. The X-axis drive mechanism 112, the Y-axis drive mechanism 114, and the Z-axis drive mechanism 116 are connected to the imaging control circuit 117, and are driven based on a drive signal from the imaging control circuit 117. Yes. The alignment detection sensor 88 is connected to an XY alignment detection circuit 118, and the XY alignment detection circuit 118 is connected to an imaging control circuit 117. The line sensor 44 is connected to the Z alignment detection circuit 120, and the Z alignment detection circuit 120 is connected to the imaging control circuit 117. Thereby, detection information of the alignment detection sensor 88 and the line sensor 44 is input to the imaging control circuit 117. In addition, although illustration is abbreviate | omitted, the imaging control circuit 117 is also connected to each illumination light source 30,40,54,74,82, and it can control these light emission.

Further, the cornea photographing apparatus 100 is provided with an image selection circuit 122 that receives an image received by the CCD 28 and selects the image, and stores the image selected by the image selection circuit 122. A storage device 124 is provided as a means. In the case of the present invention, which will be described in detail below, the image selection circuit 122 does not necessarily have to acquire an image of a corneal endothelium image within a focus position of the imaging optical system 20 within an allowable range of the endothelial cell position in the cornea C. Not necessary.

Next, in the corneal imaging device 100 having such a structure, an outline of the corneal endothelium imaging procedure executed by the imaging control circuit 117 is shown in FIG.

First, in S1, the alignment (XY alignment) of the apparatus optical system 10 in the X direction and the Y direction is performed on the eye E. During such XY alignment, the fixation target light emitted from the fixation target light source 74 is guided to the eye E. Then, by fixing the fixation target light applied to the subject, the optical axis direction of the eye E can be matched with the direction of the optical axis O1 of the observation optical system 12. Under such a state, the light beam irradiated from the observation light sources 30 and 30 and reflected by the anterior eye portion of the eye E is guided onto the CCD 28. As a result, as shown in FIG. 5, the anterior segment of the eye E is displayed on the display screen 110.

Further, on the display screen 110, for example, an alignment pattern 125 having a rectangular frame shape generated by a superimpose signal or the like is displayed over the eye E. At the same time, the light beam emitted from the alignment light source 82 toward the subject eye E is reflected by the anterior eye portion of the subject eye E and guided to the CCD 28, so that the display screen 110 has the dotted alignment light 126. It is displayed. Then, the operator operates the operation stick 108 to drive the apparatus optical system 10 and adjust the position of the apparatus optical system 10 so that the alignment light 126 enters the frame of the alignment pattern 125.

A part of the light beam irradiated from the alignment light source 82 and reflected by the anterior eye portion of the eye E is reflected by the half mirror 26 and guided to the alignment detection sensor 88. The alignment light source 82 emits an infrared beam that is not recognized by the subject, thereby reducing the burden on the subject. Here, the alignment detection sensor 88 can detect the position of the alignment light 126 in the X direction and the position of the Y direction when the alignment light 126 enters the frame of the alignment pattern 125. The X direction position and the Y direction position are input to the XY alignment detection circuit 118. The XY alignment detection circuit 118 drives the X-axis drive mechanism 112 so that the optical axis O1 of the observation optical system 10 approaches the optical axis of the eye E based on the positional information in the X direction, and uses the positional information in the Y direction. Based on this, the Y-axis drive mechanism 114 is driven so that the optical axis O1 of the observation optical system 10 approaches the optical axis of the eye E to be examined. Thereby, the alignment of the apparatus optical system 10 with respect to the eye E in the XY directions is performed. As will be described later, such XY alignment is performed at an appropriate timing even during imaging. Particularly in the present embodiment, the alignment light source 82 and the observation light sources 30 and 30 are alternately blinked in a short time, and detection by the alignment detection sensor 88 is performed in accordance with the lighting timing of the alignment light source 82. ing. As a result, the infrared light beams of the observation light sources 30 and 30 are not affected during the XY alignment. The blinking of the alignment light source 82 and the observation light sources 30 and 30 is performed at a higher speed than the conversion speed of the CCD 28 into the light reception signal. 30 is not recognized by blinking, and the light source 82, 30 is recognized as being continuously lit.

Next, in S <b> 2, the Z-axis drive mechanism 116 is driven, and the apparatus optical system 10 is moved forward in a direction approaching the eye E to be examined. Thus, in the present embodiment, the pre-imaging advance control means is configured including S2 and the Z-axis drive mechanism 116. Then, the observation light source 54 is caused to emit light, and the infrared light beam irradiated from the observation light source 54 is irradiated obliquely onto the cornea C of the eye E, and the light beam reflected from the cornea C is Light is received by the sensor 44. In particular, in this embodiment, since the light beam emitted from the observation light source 54 is an infrared light beam, the burden on the subject is reduced.

The infrared light beam from the observation light source 54 is reflected with a different amount of reflected light for each layer of the cornea C, such as epithelial cells of the cornea C, corneal stroma, and corneal endothelium. As schematically shown in FIG. 6, the infrared light beam L from the observation light source 54 is first reflected by the epithelial cells e that form the boundary surface between the air and the cornea C. Further, a part of the light beam transmitted through the epithelial cell e is reflected by the corneal stroma s and the corneal endothelium en. The amount of the reflected light beam e ′ reflected by the epithelial cell e is the largest, the amount of the reflected light beam en ′ reflected by the corneal endothelium en is relatively small, and the reflected light beam s ′ reflected by the corneal substance s. The light intensity is the smallest. Further, since the anterior chamber a is filled with aqueous humor, the infrared light beam L is hardly reflected in the anterior chamber a.

These reflected light beams are detected by the line sensor 44, and the light quantity distribution as shown in FIG. In FIG. 7, the first peak portion 128 having the largest amount of light indicates the reflected light from the corneal epithelium. Next, the second peak portion 130 with the largest amount of light indicates the reflected light from the corneal endothelium. Then, the imaging control circuit 117 drives the Z-axis drive mechanism 116 to set a predetermined distance that is an average value of the physiological cornea thickness of the human eye from the position of the corneal epithelium detected by the line sensor 44. : D1 (distance from the corneal epithelium to the corneal endothelium, about 500 μm), the apparatus optical system 10 is driven forward in a direction approaching the cornea C. The moving distance from the corneal epithelium is appropriately set at around 500 μm. Thereby, the focusing position of the imaging optical system 20 in the apparatus optical system 10 is set in the vicinity of the endothelial cell position in the cornea C.

Next, when the in-focus position of the imaging optical system 20 in the apparatus optical system 10 is set near the endothelial cell position in the cornea C, the observation light sources 30 and 30 are turned off and the imaging light source 40 emits light in S3. The imaging of the corneal endothelium is started.

When photographing of a corneal endothelium image is started, the peak value of the corneal endothelium reflection signal is acquired by the line sensor 44 in S4.

In S5, the peak value of the acquired corneal endothelial reflection signal is compared with a predetermined value. The peak value of the corneal endothelial reflection signal has a maximum value when the focus position of the imaging optical system 20 in the apparatus optical system 10 is at the endothelial cell position in the cornea C, and decreases when the position deviates from the endothelial cell position. Here, the predetermined value is a peak value of the corneal endothelial reflection signal that the in-focus position of the imaging optical system 20 is within the allowable range of the endothelial cell position in the cornea C, and may be a preset value or during imaging. It may be a value set based on the maximum value of the peak value of the corneal endothelium reflection signal detected in (1).

If it is determined in S5 that the peak value of the corneal endothelial reflection signal is smaller than the predetermined value by the line sensor 44, it is determined that the focus position of the imaging optical system 20 has shifted from the endothelial cell position in the cornea C, and the line is determined in S8. The Z-axis drive mechanism 116 is driven so that the peak position of the corneal epithelial reflection signal from the sensor 44 is at a predetermined position, and the apparatus optical system 10 is moved in the Z direction. Here, the predetermined position is the peak position of the corneal epithelial reflection signal of the line sensor 44 when the in-focus position of the imaging optical system 20 is at the endothelial cell position in the cornea C, and the movement distance (from the epithelium) moved in S2. A position of about 500 μm). That is, in S8, the apparatus is moved in the Z direction so that the focusing position of the imaging optical system 20 is moved to the endothelial cell position in the cornea C.

Then, after moving the apparatus in the Z direction in S8, the peak value of the corneal endothelial reflection signal is acquired by the line sensor 44 again in S4, and the peak value is compared with a predetermined value in S5. If it is determined that the peak value of the acquired corneal endothelial reflection signal is greater than or equal to the predetermined value, it is determined that the in-focus position of the imaging optical system 20 is the endothelial cell position in the cornea C or within an allowable range, and S6 The image of the corneal endothelium image is acquired by and stored in the storage device 124.

In FIG. 9, when the focusing position of the imaging optical system 20 is at the endothelial cell position in the cornea C ((a) and (c)), and when the eye to be examined moves slightly forward ((b) and (d) ) Shows the Z alignment state and the output waveform of the line sensor 44. P0 in (c) and (d) determines that the in-focus position of the imaging optical system 20 is within an allowable range of the endothelial cell position in the cornea C (a range of positions where a high-contrast endothelial cell image can be acquired). This is a predetermined value (light quantity value) on the line sensor 44 of the reflected light. (A) When the in-focus position of the imaging optical system 20 is within the allowable range of the endothelial cell position in the cornea C, as shown in (c), the peak value P1 of the corneal endothelial reflected light is P0 or more, b) When the eye to be examined moves and the in-focus position of the imaging optical system 20 moves beyond the allowable range of the endothelial cell position in the cornea C, as shown in (d), the peak value P1 of the corneal endothelial reflected light is It becomes smaller than P0. Thus, by comparing the peak value P1 of the corneal endothelium reflected light with the predetermined value P0, the Z alignment state (whether the in-focus position of the imaging optical system 20 is at the endothelial cell position in the cornea C) can be grasped, Since the Z alignment is automatically performed when the Z alignment is deviated as described above, the corneal endothelium of the eye to be examined is always in a good state (the focal position of the imaging optical system 20 is at the endothelial cell position in the cornea C). A cell image can be acquired. (In FIGS. 9 (a) and 9 (b)), the light beam of the observation light source 54 (the position detection illumination optical system 18 in the figure) is actually incident on the cornea C and reflected from the endothelial cells. When radiating from C, it is refracted slightly by the corneal epithelium e, but the refraction state is omitted for the sake of easy understanding.)

The predetermined value P0 may be a preset value obtained from an eye more than a certain value, or the maximum value of the peak value P1 of the corneal endothelium reflected light is stored during imaging, and is based on the stored maximum value of the peak value P1. The value set by

As mentioned above, although one embodiment of the present invention has been described in detail, the present invention is not limited in any way by the specific description in the embodiment, and various changes, modifications, and modifications based on the knowledge of those skilled in the art. Needless to say, the present invention can be implemented in a mode with improvements and the like, and all such modes are included in the scope of the present invention without departing from the gist of the present invention.

10: device optical system, 12: observation optical system, 14: imaging illumination optical system, 16: position detection optical system, 18: position detection illumination optical system, 20: imaging optical system, 28: CCD, 30: light source for observation, 40: imaging light source, 44: line sensor, 54: observation light source, 64: fixation target optical system, 66: alignment optical system, 74: fixation target light source, 82: alignment light source, 84: alignment detection optical system, 88: Alignment detection sensor

Claims (3)

An imaging optical system including an illumination optical system including an illumination light source that irradiates the slit light beam obliquely to the eye to be examined, and a photoelectric element that receives a reflected light beam from the cornea of the eye to be examined by the slit light beam and captures a corneal image And
In the cornea photographing apparatus provided with a driving unit that moves the illumination optical system and the imaging optical system as a whole toward or away from the eye to be focused,
It includes a light source and a light receiving element for detecting front and rear positions (positions of Z-axis coordinates),
The light receiving element receives reflected light from the corneal endothelium and epithelium of the eye to be examined,
Detects the peak value of the endothelium reflection signal,
A corneal imaging apparatus comprising control means for moving the apparatus back and forth (in the Z-axis direction) so that the peak position of the epithelial reflection signal moves to a predetermined position when the detected peak value is lower than a predetermined value. 2. The cornea according to claim 1, wherein the predetermined value is stored based on the maximum value of the amount of reflected light of the corneal endothelium received by the light receiving element during corneal endothelial cell imaging, and is set based on the stored maximum value. Shooting device. The corneal imaging apparatus according to claim 1, wherein the predetermined position is a distance from a corneal epithelium position to a corneal thickness (about 500 μm).